April 23, 1998 – Phytoestrogens are a group of natural products derived from certain plants, including soy. They have a structure similar to estrogen and are part of our diet. They are associated with an anticarcinogenic biological activity. The purpose of the following study was to determine the association between the consumption of phytoestrogens (measured by urinary excretion) and the risk of breast cancer.
The study was carried out on 144 women in the city of Perth (Australia) who had just been diagnosed with breast cancer. The control group consisted of an equal number of women of comparable age and place of residence.
After adjustment for the age of the first period (menarche), the age of the first pregnancy, menopause, hormone therapy, family history of breast cancer, alcohol and fat consumption, and a few others Factors likely to influence the results, the excretion of enterolactone and equol (two types of phytoestrogens) was associated with a substantial decrease in the risk of breast cancer. For the other types of phytoestrogens (enterodiol, mataresinol, daidzein and genistein), the reduction in risk was observable without reaching a significant difference.
The researchers’ conclusions are that women with a high intake of phytoestrogens (particularly isoflavone equol and lignan enterolactone) are relatively less likely to develop breast cancer. This discovery, they say, may be important in preventing breast cancer.
However, the study only looked at a measure of phytoestrogen consumption at a specific point in the participants’ lives and it is possible that this measure changed during their lifetime. Critics of the study therefore point to the fact that a causal link between the consumption of phytoestrogens and the risk of breast cancer has not been demonstrated.
Case-control study of phyto-oestrogens and breast cancer, Ingram D, Sanders K, Kolybaba M, Lopez D., Lancet 1997; 350: 990-994
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From Alternative Therapies in Health and Medicine, January 1998, vol 4, no 1 and L’Actualité Médicale, April 15, 1998.